Gene Therapy Offers Hope to Infertile Men
May 31, 2002 -- A new form of gene therapy may eventually help infertile men become fathers. Researchers say they were able to correct a common cause of male infertility by using the new technique in mice that previously couldn't produce sperm.
The report appears in the May 28 issue of the Proceedings of theNational Academy of Sciences.
According to researchers, about one in five couples worldwide are infertile. About 30-50% of infertility cases are caused by male fertility problems, such as sperm production issues. But for most men, the problem isn't that they can't produce any sperm cells, it's that the cells they do produce don't fully mature.
Immature sperm are called germ cells. They require the help of other cells, such as Sertoli cells, to help them grown into sperm. If those cells aren't working properly, the germ cells never mature, and infertility is the result.
In the study, researchers were able to correct the gene mutation that caused the Sertoli cells of infertile mice to malfunction. The technique involved attaching a good copy of the gene to a harmless virus, which carried the good gene into the body. Once in, the gene directed the Sertoli cells to begin functioning properly.
Two months after treatment, the mice began to produce sperm. Mice did not produce enough sperm to impregnate a female naturally or by a process known as in vitro fertilization (when sperm and egg are joined in a test tube). But researchers were able to create embryos by injecting individual sperm directly into the eggs. This technique is also used in humans in cases where the man cannot produce enough sperm.
By the end of the study, 13 healthy mice pups were born through this process. Researchers say none of the offspring showed any signs of infection with the altered virus that served to transport the gene.
In addition, none of the mouse pups inherited the repaired gene. The study authors say that's important because it shows that they were able to repair the mutated gene without having any impact on the DNA of the offspring.
Before the technique can be used in men, however, researchers must be able to identify which genes are causing the malfunctioning of the sperm development process in humans. Then, a repair plan can be developed.
"Gene therapy approaches, along with germ cell transplantation and assisted fertilization techniques, offer a potential ... treatment for male infertility," write the study authors.